Composition of Commercial Bis(2-ethylhexyl) Sulfosuccinate Surfactant By-Products and their Effects on an Agrochemical Formulation

Sodium bis(2-ethylhexyl) sulfosuccinate (known as AOT) is a commercially available surfactant commonly used in agrochemicals. Besides the principal diester surfactant, the commercial AOT product contains two surface-active isomeric monoester by-products, which may influence the surfactant’s overall properties. This work investigates whether the purity of the surfactant affects its ability to stabilize an agrochemical formulation. The concentrations of the diester and two monoester impurities in batches of commercial AOT product from several suppliers were determined quantitatively by liquid chromatography–mass spectrometry. The tested batches showed different contents of the monoesters. Samples of a model agrochemical formulation containing the AOT product formed more sediment during storage when the content of monoesters in the surfactant was high. The supplier of an commercial AOT product could be traced by analysis of the monoester content of either the raw product or the aged agrochemical formulation.